Temperature responsive controller



Jan; 1946 A. c. PURPURA 2,392,407

TEMPERATURE RESPONS IVE CONTROLLER Filed April 24., 1942 k, i W i 5. 5

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Patented Jan. 8, 1946 UNITED STATES PATENT OFFICE 2,392,407 TEMPERATURE RESPONSIVE CONTROLLER August 0. Purpura, Chicago, 111., assignor to Chicago Flexible Shaft Company, Chicago, 111., a corporation of Illinois Application April 24, 1942, Serial No. 440,273

I lug 5, in screwthreaded relation to the latter, and

16 Claims.

The present invention has for its object to produce a simple, novel, eflicient, sensitive controlling device responsive to variations in temperature, and one which may be accurately adjusted, by a simple manipulation, over a wide range.

In carrying out my invention I mploy a novel form of bimetallic strip which provides a snap action in the operation of the controller and, therefore, the present invention may be said to have for an object the creation of a novel bimetallic element which has a snap action in response to temperature changes.

The various features of novelty whereby my invention is characterized will hereinafter be pointed out with particularity in the claims; but, for a full understanding of my invention and of its objects and advantages, reference may be had to the following detailed description taken in connection with the accompanying drawing, wherein:

Figure 1 is a side elevation of a controller embodying the present invention, the base or the support for the controller elements being shown in section; Fig. 2 is a section on line 22 of Fig. 1; Fig. 3 is a section on line 33 of Fig. 1; Fig. 4 is a section on line 4-4 of Fig. 1; Fig. 5 is an edge View of a modified form of bimetallic strip; Fig. 6 is an edge view of a further modification of the strip; Fig. 7 is an edge view of a still further modified form of strip illustrating a compensating means carried by or forming part of the same; and Fig. 8 is a section through an electric iron, illustrating the manner in which the controlling device may be mounted therein.

Referring to Figs. 1 to 4 of the drawing, l represents a base which may be a narrow fiat member having a central slot 2 extending inwardly from one end thereof to a point not far from the opposite end. From the latter end of the base rises a little pedestal 3 having at the lower end an inward projection 4; a similar projection 5 being formed at the upper end of the pedestal so as to overlie the projection or lug 4. At the opposite end of the base are a pair of ears 6 rising upwardly from opposite sides of the slot. Arranged between the ears 6, pivotally secured thereto by a pin l, is a part 8 which, for the sake of lightness, may comprise a piece of heavy sheet metal of U-=shape. From one wing or flange of the part 8 extends a long arm 9 that reaches into the vicinity of the pedestal 3; this arm lying at some distance above and roughly parallel to the base. Secured to the free end of the arm 9 is a bimetallic strip I!) that underlies the lug or projection 5. A screw ll extends down through the it is connected to the part In so that the latter must move '1 and down with the screw although the screw is rotatable therein. It will thus be seen that by turning the screw, the lever which comprises th parts 8 and 9 may be rocked through a small angle.

The lug or projection 4 and the part 8 serve as abutments or anchors for the ends of a temperature-responsive bimetallic strip l2 which possesses novel features aside from the settin therefor. The novel characteristic of this strip is that it constitutes a bow which has a reentrant bend at the middle, or in other words, that is composed of two bow-like sections meeting end to and. The metal having the higher coefficient of expansion is on the under or concave side of the strip. The strip may conveniently be mounted on it support by fashioning the ends into knife edges that may be engaged in notches i4 and I5 in the abutments or anchors. It will be seen that by properly proportioning the parts, the strip l2 may be caused ib-be under any desired initial,,stress when the parts of the controller as a whole are assembled. Then, by adjusting the screw I l the tension may be increased or decreased, by rocking the pivoted abutment. Consequently the strip may be caused to act as a spring in conjunction with and under the control of the flexing brought about by temperature changes, the central portion snapping down, as viewed in Fig. 1, when the strip is heated to a predetermined temperature; the degree of temperature required to produce this action bein determined by the adjustment of the movable abutment 8.

The arm 9 is provided at about the middle with an ear it that extends above and across the strip 12. A set screw I'l extends through this ear and engages in the valley on the back side of the strip, namely at the juncture of the two bow-shaped sections. The parts are so proportioned that at room temperature the middle of the strip lies well inwardly from a line connecting the two ends. Then, when the strip is heated, in use, stresses are built up therein, due to the unequal expansion of the two metal layers, until, finally, the strip flexes suddenly and the middle portion snaps to or past the line or chord extending between the two ends thereof. This snap action maybe utilized to effect a quick turns to its normal idle position. The drop in temperature which must ensue to cause restoration of the strip varies, for a given initial stress in the strip, according to how far the middle of the strip is permitted to be deflected. For some purposes the temperature drop should be small while for others it may be caused to be much greater, Thus, in the case of an electric iron, silk goods should be ironed at a low temperature and the temperature fluctuation should be small while ironing. On the other hand, woolen goods must be ironed at much higher temperatures and a much wider range temperature fluctuations during ironing is permissible. In the construction illustrated, there is arranged in the slot, 2, a long light bar I8 held in place by a pin l9 that is parallel to the pin 1. One end of the bar lies below the center of the bimetallic strip, while the other end underlies the lug l; the hinge pin is being not far from this latter end. The screw,

II is provided with a rod or stem 20, coaxial therewith, extending down through the lug t and engaged with the top of the short arm of the rocker member I8. The free end of the long arm of the member 3 serves as a stop which is engaged by the central portion of the strip when the strip snaps down. It will be seen that although both the upper and lower stops for the bimetallic strip are adjusted simultaneously through the screw II, the extent of adjustment of the lower stop is much the greater, because the upper stop moves up and down only about one half as far as does the screw ll, whereas the movement of the screw is greatly multiplied for the lower stop.

The movement of the bimetallic member is utilized to open a switch 2| in the arrangement illustrated in Fig, 1, whenever the strip is heated to the proper temperature. This is done by mounting in the slot 2 a second elongated rocker 22 which is hinged to the base by a pin 24 near the extreme end of the base out'of which the slot opens. A short arm element 25 of the rocker member 22 projects outwardly beyond the base and carries a little post'26 of insulating material the upper end of which underlies the movable member of the switch. The long arm of the rocker 22 extends to a point near the middle of the bimetallic strip and close enough to the strip to insure contact with the same before the strip engages the stop member l8, in any position of adjustment of the latter. When the strip snaps down, it strikes a sharp blow against the rocker 22 and causes the switch to be opened quickly,

The member In may be simply a part of the rocking lever 8, 9 or it may be a bimetallicelement adapted to compensate for slow heating of the strip when the electric iron or other device containin the same first goes into use. For example, the sole of an electric iron. usually heats up much more quickly than does the main thermostat, upon turning on the current. Therefore, the iron may be too hot when ironing the first piece of a batch of laundry. By employing a compensating thermostat in the form of the part H), which will heat up rapidly, the initial stress on the thermostat [2 maybe reduced and thus permit the current to be interrupted when the sole of the iron reachesor passes the desired temperature. Thereafter, as the main thermostat becomes more effectively heated it functions properly at the higher temperature.

In-Fig. 8 the device is shown installed in an electric iron 21, the screw I! having thereon a finger piece 28 which is the only part of the device visible or accessible to the user of the iron.

By simply turning the finger piece, the user is enabled to control the maximum temperature of the iron and the degree of fluctuation of temperature while in use. The higher the temperature desired, the greater is the extent of flexing of the bimetallic strip l2 and the drop in temperature required to shut off the current during ironing. When ironing light goods, at low temperature, the temperature of the sole of the iron usually does not drop rapidly and, therefore, the temperature may be kept within a range of only a few degrees without constant opening and closing of the switch. When ironing heavy woolen goods, at high temperatures, on the other hand, the temperature of the sole of the iron may drop quickly as much as forty or fifty degrees and rapidly rise again. Therefore, in such use, if it were attempted to keep the temperature within a few degrees, the switch would be opening and closing incessantly,

Since the main bimetallic strip in effect consists of two connected units, the two layers of metal need not be continuous from one end of the strip to the other, but only throughout each section; the connection between the two sections being of any suitable character. Thus, in Fig. 5, the strip is formed of a continuous layer 29 and a second layer that is interrupted at the juncture of the two sections; the second layer being in two pieces 30, each completing one of the bow-shaped sections.

In Fig. 6 only one of the two connected sections is bimetallic, the layer 29 being continuous throughout the length of the strip, while the layer 3!] is only as long as and coextensive with one of the sections.

In Fig. 7, the bimetallic strip 3! ls=similar to that in Fig. 1 except that one section is shorter than the other and is brought up to the full length of the latter by an attached compensating bimetallic element 32 secured thereto. In this construction the layer of metal having the high coeflicient of expansion is on the concave side of the main strip and on the convex side of the compensating element. There is also here illustrated a guard plate 33 overlying the compensating element and spaced apart therefrom throughout the effective portion of the latter, to shield it' against the heat radiated from some near by heating element.

I claim: I

1. A controlling device responsive to temperature changes comprising a strip in the form of a bow in which there are two bow-shaped sections arranged end to end interconnected by a V-shaped center section at least one of said bowshaped sections being of bimetallic material, the meeting point of the two sections lying normally inwardly from a line connecting the endsoi the strip, stationary anchors for the ends of the strip, and a stop for engaging with said strip after the said strip is flexed to carry said meeting point toward or across said line,

2. A controlling device responsive to temperature changes comprising a strip in the form of a bow in which there are two bow-shaped sections arranged end to end interconnected by a V-shaped center section, at least one of said bow-shaped sections being of bimetallic material, the meeting point of the two sections lying inwardly from a line connecting the ends of the strip when the strip is unrestrained, stationary anchors for the ends of the strip, and adjustable stops for alternately engaging with opposite sides of the strip when it is stressed to bring said meeting point to any desired distance on one side or the other of said line.

3. A controller responsive to temperature changes comprising a strip in the form of a bow in which there are two bow-shaped sections ar-= ranged end to end and interconnected by a V-shaped section having its v point lying inwardly from a line connecting the ends of the strip when the strip is unrestrained, at least one of said bow-shaped sections being of bimetallic material, stationary anchors for the ends of the strip, a stop for engaging when the latter is heated and caused to flex until the middle thereof is shifted through a predetermined distance toward said line, a switch, and a switch actuator extending into the path of'a movable portion of the strip before the latter engages the stop.

4. A controller responsive to temperature changes comprising a bimetallic strip in the form of a bow in which there are two bow-shaped sections arranged end to end and meeting at the middle of the strip at a point lying inwardly from a line connecting the ends of the strip when the metal having the higher coefficient of expansion being on the concave-side of the strip, the strip is unrestrained, stationary anchors for the ends of the strip, a stop for engaging the strip when it is flexed to carry the middle portion thereof any desired distance in the direction of said line, and means simultaneously to adjust said stop and vary the distance between said anchors.

5. A controller responsive to temperature changes comprising a strip in the form of a bow in which there are two bow-shaped sections arranged end to end and meeting at the middle of the strip at a point lying inwardly from a line connecting the ends of the strip when the strip is unrestrained, at least one of said bow-shaped sections being of bimetallic material, stationary anchors for the ends of the strip, adjustable stops for alternately engaging with opposite sides of the strip when it is flexed first in one direction and then in the other, and means simultaneously to spread said anchors and move said stops toward each other or to cause the anchors to approach nearer each other and the stops to recede from each other.

6. A controller responsive to temperature changes comprising a strip in the form of a bow in which there are two bow-shaped sections ar-= ranged end to end and meeting at the middle of the strip at a point lying inwardly from a line connecting the ends of the strip when the strip is unrestrained, at least one of said bow-shaped sections being of bimetallic material, stationary anchors for the ends of the strip, a stop for engaging with the strip when it is flexed to carry the middle portion thereof a predetermined disspread apart when said means becomes heated to a higher temperature than that of the strip.

8. A controller responsive totemperature variations comprising a generally bow-shaped strip, abutments engaging the ends of the strip and serving to support the strip, the strip shaped to provide two bow-shaped sections each extending from the center of the strip to an opposite end and supported at such end on the adjacent abut ment, each section being bowed toward that side of the strip to which the strip as a whole is bowed, at least one of said bow-shaped sections being bimetallic, adjustable stops defining a gap between which the center portion of the strip is movable in a snap action in opposite directions in response to heating and cooling, and means for adjusting said stops to provide a relatively wide gap for operating at a high temperature setting and to provide a relatively narrow gap for operating at a low temperature setting.

9. A controller responsive to temperature variations as set forth in claim 8, including means Kill] tance in the direction of said line, and means including a temperature-responsive compensating device simultaneously to adjust said anchors from or toward each other and the stop away from or toward the strip.

7. A controller responsive to temperature changes comprising a strip in the form of a bow in which there are two bow-shaped sections arranged end to end and meeting at the middle of the strip at a point lying inwardly from a line connecting the ends of the strip when the strip is unrestrained, at least one of said bow-shaped sections being of bimetallic material, stationary anchors for the ends of the strip, and a temperature responsive means to cause said anchors to for stressing the strip lengthwise thereof to change the point at which snap action will occur.

10. A controller responsive to temperature variations as set forth in claim 8, including means for stressing the strip lengthwise thereof to change the point at which snap action will occur and including means for varying said compressive stress simultaneously with and in proportion to the adjustment of said stops.

11. A controller responsive to temperature variations as set forth in claim 8, including a compensating thermostat attached to one of the bowshaped sections.

12. In a heat responsive controller having a bimetallic strip supported at each end, the center portion of the strip being formed into a V-shape and the remaining portions of the strip being formed'into two bow-shaped sections, said sections being interconnected by said V-shaped center portion, the said V shaped center portion adapted to move up and down in snap action movements in response to heating and cooling, stationary and movable supports for supporting the bimetallic strip at its ends, and a manual adjustment for moving the movable support toward and away from the stationary support for placing the bimetallic strip under tension and for vary ing said tension, the tensioning action tending to hold the bimetallic strip in the above described form, said snap action being theresult oi defleet-ion of the entire strip and independent lengthwise compression of the individual howshaped sections to allow variation in length of said individual sections incident to lengthwise compression forces when the entire strip deflected.

13. A controlling device responsive to temper ature changes comprising a bow-shaped strip, abutments engaging the ends of the strip and serving to support the strip, the strip shaped to provide two bow-shaped sections each extending from the center of the strip to an opposite end and supported at such end on adjacent said abutment, the entire strip'being bimetallic except for a gap at the juncture of said bowshaped sections formed by omission oi. one of the i metals of the bimetallic strip, said center portion of the strip being adapted to deflect in snap action movements in response to heating and cooling.

1a. In a heat responsive controller, in com- I bination, a circuit controlling switch, a bimetallic strip mounted so as to have snap action move operating said switch, manually adjustable means coacting with the bimetallic strip for determining the temperature at which said bimetallic strip shall actuate, said switch, and additional means operated by said manually adjustable means coacting with the bimetallic strip to vary the gap through which the bimetallic strip moves thereby varying the efiective working stroke of the bimetallic strip, said adjusting means being constructed and arranged so that the working stroke gap of the bimetallic element shall be wider in order to open and close said switch when the manual adjustment is set for higher temperature control and the working stroke gap of the bimetallic strip shall be smaller when the manual adjustment is set for lower temperaturecontrol.

15. A heat responsive device comprising a thermostat strip supported so as to flex laterally in response to changes in temperature and being under longitudinal compression so as to have snap action, means for varying said longitudinal compression, means for limiting said lateral movement of the strip acting against opposite sides of the strip and being adjustable to vary the gap through. which the strip moves, manually operable means adapted to be set for predeordinating the described means whereby the adjustment of said manually operable means in one direction serves to increase said longitudinal compression and simultaneously widen said gap, and whereby adjustment in the opposite direction serves to decrease said compression and narrow said gap,

' 16. A heat responsive device comprising a thermostat strip supported so as to flex laterally in response to changes in temperature and being under longitudinal compression so as to have snap action, means for varying said longitudinal compression, means for limiting said lateral movement of the strip acting against opposite sides of the strip and being adjustable to vary the gap through which the strip moves, manually operable means adapted to be set for predetermined temperature settings, and means coordinating the described means whereby the adjustment of said manually operable means in one direction serves to increase said longitudinal compression and widen said gap, and whereby adjustment in the opposite direction serves to decrease said compression and narrow said gap.

AUGUST C. PURPURA. 

